The invention relates to a piezoelectric ceramic transistor. More particularly, the invention provides an electric element that is suitable for use in piezoelectric converter device, and can increase electric power.
As shown in the schematic views of FIG. 1 and FIG. 2, present driving devices for driving cold cathode fluorescent lamp (CCFL) comprises a driving device and a CCFL driven by the driving device. The driving device comprises a power supply unit 1, a pulse width modulation (PWM) control unit 2, a driving unit 3, and a piezoelectric ceramic voltage transformer 4xe2x80x2. The CCFL 7 connects to the PWM 2 through a current feedback 5 and the piezoelectric ceramic voltage transformer 4xe2x80x2 connects to the PWM 2 through the voltage feedback 6. When this driving device is turned on and inputs a voltage, the driving unit 3 immediately drives the piezoelectric ceramic voltage transformer 4xe2x80x2 that in turn drives the illumination of the CCFL 7 via piezoelectric ceramic reverse effect. The PWM control unit 2 then detects the average output current intensity of the CCFL 7 through current feedback 5 to output a resonance frequency. The resonance frequency via the control unit 3and the piezoelectric ceramic voltage transformer 4xe2x80x2 can control the average current of the CCFL 7. Hence, the light source generated from the CCFL 7 is projected on the semi-transparent back panel to illuminate the back panel and match the display frame of the LCD screen. Because the illumination of the CCFL 7 via driving of the above driving device is limited or uniform, several CCFL 7 are therefore needed to obtain a uniform back panel illumination of the LCD screen. As a result, the fabrication cost is increased, and the fabrication process further is not easily achieved.
It is therefore an object of the invention to provide a piezoelectric ceramic transistor that can overcome the above problems by being fabricated from a single-layered or multi-stacked layers piezoelectric ceramic voltage transformer that has an input terminal series connected to a capacitor. The above capacitor thereby forms a bypass capacitor that increases the power and prevents a loss due to feedback so that vibrations of the piezoelectric ceramic voltage transformer are compensated. Alternatively, the above connection scheme is achieved by either serial connecting a capacitor between a power output of the transformer and a load terminal, or parallel connecting a first capacitor to a power input of the transformer while a second capacitor is series connected between a power output of the transformer and the load terminal to obtain an increased power and thereby increasing the load current.
Another object of the invention is to provide a piezoelectric ceramic transistor that is formed either via the connection of traditionally known electric elements or via semiconductor packaging into a single element.
Furthermore, another object of the invention is to provide a piezoelectric ceramic transistor that can reduce the number of CCFL mounted to the LCD screen so that the fabrication is facilitated and the fabrication cost reduced.
Still, another object of the invention is to provide a piezoelectric ceramic transistor that can allow CCFL with higher power or of longer length, or CCFL drive with lower driving voltage.
To provide a further understanding of the invention, the following detailed description illustrates embodiments and examples of the invention, this detailed description being provided only for illustration of the invention.